Method for producing super smooth photo plates

ABSTRACT

A supersmooth photo-plate is produced by utilization of a prefabricated photographic film, from which the photo-emulsion layer is severed by submitting said photographic film to a &#39;&#39;&#39;&#39;severing&#39;&#39;&#39;&#39; solution. The severed photo-emulsion layer is applied to a very smooth carrier. The resulting photo-plate possesses an even overall thickness and can assume stable values from 1 to 10 Mu .

States Patent Feb. 18, 1975 METHOD FOR PRODUCING SUPER SMOOTH PHOTO PLATES [75] Inventor: Franz Klapper, Jena, Germany [73] Assignee: Jenoptik Jena G.m.b.ll Jena,

District of Gera, Germany 22 Filed: Jan. 12, 1973 21 Appl. No.: 323,200

2,182,814 12/1939 Marasco 96/83 2,386,602 10/1945 Gloseffi 96/83 X 2,489,987 11/1949 Barnola. 156/235 X 2,604,398 7/1952 Soper 96/83 2,670,312 2/1954 Capstaff.... 156/235 3,334,003 8/1967 Edwards 156/249 X 3,607,346 9/1971 Darlow et al.. 96/83 X Primary ExaminerCharles E. Van Horn Assistant Examiner-Th0mas E. Bokan [57] ABSTRACT A supersmooth photo-plate is produced by utilization of a prefabricated photographic film, from which the photo-emulsion layer is severed by submitting said photographic film to a severing solution.

The severed photo-emulsion layer is applied to a very smooth carrier. The resulting photo-plate possesses an even overall thickness and can assume stable values from 1 to 10 ,u..

3 Claims, 6 Drawing Figures a bare apply a photaemulsion to layer wash the photoemu lsion Carrier apply saicl photoemuLs/an layer to a "supersrnooth" press the pholoemulsion layer to the carrier cutoff the edge portions of the phatoemulsi'on layer hanging over the carrier drying dewoter the pholoemutsion layer by blasting and resultin hoto p ale supersm 00 th PATEN TED FEB I 8 I975 appty a. pholaemutsion' (0 a bare treat the sample in a parting sotution and subsequent strip photo layer from its 190% wash the photoemutsion (ayer I apply said photoemutsion tayer to a "supersmooth" Carrier press the photo emutsion layer to the carrier cut off the edge portions of the photoemutsi'ontayer hanging over the carrier devvater the photoemutsion (ayer by blasting and drying rest/(tin 5uper5moat photo p ate Fig. 7

7 to vacuum mama pump METHOD FOR PRODUCING SUPER SMOOTH PHOTO PLATES This invention concerns a method for producing supersmooth photo-plates, the photo-emulsion layer thereon having an equal overall thickness, which can have stable values from I to 10 microns. Such photoplates are particularly suited for recording microstructures, in micro-electronics, for example photo-masks. They may also be applied for recording holograms and optical grids. With the heretofore methods photoplates are produced by coating a carrier, preferably glass, with a photo-emulsion. After drying the emulsion layer, the carrier is cut to the desired sizes. Owing to the cutting action undesired tensions are provoked within the glass, leading to considerable warpage,

which in turn causes picture distortions in a later record. Furthermore, it has not yet been accomplished to evenly coat a pre-fabricated carrier material with a liquid photo-emulsion. Accordingly the surface of the liquid emulsion, clue to the inherent surface tensions, declines towards the edge portions, resulting in a slope or bulged region of about to mm width, in the dried state. Therefore it is difficult to define a recording area, which is suited for and required by the micro-precise recording techniques for producing, for example, photo-masks.

It is an object of the present invention to obviate the above disadvantages.

It is a further object to provide a method for producing a supersmooth photo-plate, by the application of which method a preselected size carrier is coated with a photo-emulsion layer of equal thickness on its entire surface. Accordingly, the present invention is in concern of a method for producing a supersmooth photoplate comprising the steps of severing the photoemulsion layer from a carrier after submitting a prefabricated photographic film to an aqueous hydro-fluoric acid bath containing 0.1 to 0.4 per cent hydrofluoric acid, washing the stripped off photo-emulsion layer in distilled water in order to remove impurities and residual hydro-fluoric acid, subsequent applying said photoemulsion layer on a clean and very smooth carrier, and cutting off the portions of the photo-emulsion layer projecting over the carrier, removing the residual water from said photo-emulsion layer by means of a pressuregas stream and finally drying the resulting very smooth photo-plate at a temperature of about 30C. Preferably, the prefabricated photographic film is immersed into said 0.1 to 0.4 percent aqueous hydro-fluoric acid bath for about seconds, in order to expedite the action of severing said photo-emulsion layer from said carrier. Furthermore, the inventional method provides means for removing said photo-emulsion layer from the distilled water bath and for applying said photo-emulsion layer to and pressing it on said very smooth carrier.

In order that the invention may be more readily understood, reference is made to the accompanying drawings which illustrate diagrammatically and by way of example the method and embodiments thereof, and in which FIG. 1 is a chart illustrating the most important steps of the inventional method.

FIG. 2 shows schematically a severing" bath,

FIG. 3 and FIG. 4 exemplify the operation of coating a carrier with the photo-emulsion layer.

FIG. 5 represents the process of pressing the photoemulsion layer onto the carrier and FIG. 6 shows a device for cutting off those portions of the photo-emulsion layer which project over the carrier.

FIG. 1 shows the operation sequence of the method, in which as a first step a carrier is coated with a liquid photo-emulsion layer. After congealing and drying, the layer is cut into desired sizes, thus forming the individual photo-plates. Subsequent thereto, as shown in FIG. 2, the individual photo-plates l are immersed into a bath 2 for severing a photo-emulsion layer 3 from a carrier 4. The bath which effects the disconnection is composed of aqueous solution containing 0.1 to 0.4 percent hydro-fluoric acid. By immersing the photo-plates into the bath, the adhesive forces between the photoemulsion layer and the carrier are decomposed or destroyed. As a consequence thereof the photo-emulsion layer peels off. The solution does substantially not affect the photographic properties of the emulsion layer, such as speed, grain size, fog formation and sensitization. When the photo-emulsion layer 3 has been severed, the continuous film is washed (FIG. 3) by submitting it to at least one bath of distilled water 5, in order to remove any residual hydrous fluoric acid solution, which might adhere to the film or has entered into it. Therefore it is necessary to take up said film, which action is not easily accomplished, since said film is moved even by the least water undulations. Preferably, shovel-shaped plastic siphons are used. In order to avoid wrinkle formation in the course of the washing, the film is advantageously placed on the water surface, as shown in FIG. 3, in which the surface tension of the water bath is exploited for straightening out the film. However, it is necessary to remove any water drops from the film surface before bringing it down to the water surface, since said water drops by unification with the water of the bath would cause sagging of the photo-emulsion layer, particularly of its edge portions. Said sagging would favour wrinkle formation of the film while taking it up. In order to maintain the surface tension of and to keep away impurities from the photoplates, the inventional method has entirely to be carried out under clean-room-conditions. After washing, the photo-emulsion layer 3 is removed from the bath by means of a transporter 6, which comprises a fine-mesh screen lifter 7, the orifices 8 therein having a diameter of about 0.5 mm, and a chamber 3, being rear-sidedly mounted on said lifter 7. Said chamber is connected by means of a duct 10 to a vacuum pump and to a water pump, respectively. Said transporter 6 is adjacently positioned over saidphoto-emulsion layer 3. By evacuating said chamber 9 the emulsion-layer is drawn up to and firmly held by the very smooth surface of the lifter 7. Subsequently, said transporter 6 and said emulsionlayer adhering thereto are brought to contact inclinedly one edge of a carrier 11 (FIG. 4) so that a water layer 12 thereon wets said photo-emulsion layer thus preventing air inclusions when the photo-emulsion layer is mounted on the carrier 11, which action is accomplished by tilting said transporter 6 in the direction indicated by an arrow A. In order to avoid wrinkle formation in the photo-emulsion layer, the subpressure in chamber 9 is maintained during the tilting action. As a next step the transporter 6 softly presses said photoemulsion layer to the carrier 11 (FIG. 5), secured to a mount 13, thereby the water enclosed between the carrier and the emulsion layer is expelled. Only now a stabilization of the emulsion layer is obtained and via said duct the chamber 9 is filled with pressure water, which by way of said orifices in said lifter 7 acts upon the emulsion layer and overcomes the adhesive forces between the lifter surface and said photo-emulsion layer, and, in addition thereto, the latter is pressed to the carrier 11, which is to be coated. A high degree of smoothness is required from the surface of said lifter 7 onvwhich the layercomes to rest, in order to evenly press said photo-emulsion layer 3v onto said carrier 11, and to avoid a destruction of the photo-emulsion layer which otherwise might occur owing to an undue high .local pressure. In a next operation, the transporter 6 is 4 washing the stripped off photo-emulsion layer in distilled water in order to remove impurities and residual hydro-fluoric acid, subsequent applying said photo-emulsion layer on a clean and very smooth carrier, said photo-emulsion layer projecting over the edge of said clean and very smooth carrier,

and

cutting off the portions of the photo-emulsion layer projecting over the carrier edge,

removing the residual water from said photoemulsion layer by means of a pressure-gas stream and finally drying the resulting very smooth photo-plate at a temperature of about 30C.

2. A method for producing a super-smooth photoplate as claimed in claim 1, wherein the prefabricated photographic film is immersed into said 0.1 to 0.4 volume percent aqueous hydrofluoric acid bath for about 20 seconds, in order to expedite the action of severing said photo-emulsion layer from said carrier.

3. A method for producing super-smooth photoplates as claimed in claim 1, wherein said photoemulsion layer is removed from the distilled water bath and is applied under pressure to said very smooth car- 

1. A METHOD FOR PRODUCING A SUPER-SMOOTH PHOTO-PLATE COMPRISING THE STEPS OF SEVERING THE PHOTO-EMULSION LAYER FROM A CARRIER AFTER SUBMITTING A PREFABRICATED PHOTOGRAPHIC FILM TO AN AQUEOUS HYDRO-FLUORIC ACID BATH CONTAINING 0.1 TO 0.4 VOLUME PERCENT HYDRO-FLUORIC ACID, WASHING THE STRIPPED OFF PHOTO-EMULSION LAYER IS DISTILLED WATER IN ORDER TO REMOVE IMPURITIES AND RESIDUAL HYDROFLUORIC ACID, SUBSEQUENTLY APPLYING SAID PHOTO-EMULSION LAYER ON A CLEAN AND VERY SMOOTH CARRIER, SAID PHOTO-EMULSION LAYER PROJECTING OVER THE EDGE OF SAID CLEAN AND VERY SMOOTH CARRIER, AND CUTTING OFF THE PORTION OF THE PHOTO-EMULSION LAYER PROJECTING OVER THE CARRIER EDGE, REMOVING THE RESIDUAL WATER FROM SAID PHOTO-EMULSION LAYER BY MEANS OF A PRESSURE-GAS STREAM AND FINALLY DRYING THE RESULTING VERY SMOOTH PHOTO-PLATE AT A TEMPERATURE OF ABOUT 30*C.
 2. A method for producing a super-smooth photo-plate as claimed in claim 1, wherein the prefabricated photographic film is immersed into said 0.1 to 0.4 volume percent aqueous hydrofluoric acid bath for about 20 seconds, in order to expedite the action of severing said photo-emulsion layer from said carrier.
 3. A method for producing super-smooth photo-plates as claimed in claim 1, wherein said photo-emulsion layer is removed from the distilled water bath and is applied under pressure to said very smooth carrier. 